This invention relates generally to a vehicle-starting circuit utilizing two starting batteries, and more particularly, to an improvement in this circuit for detection of excessive voltage.
In a vehicle-starting circuit in which two starting batteries are used, the batteries, being nominal 12 volt batteries, are normally connected in parallel and are used to connect and start a stalled vehicle 12 volt battery. Under normal operating conditions, the two 12 volt batteries in parallel provide a 12 volt power source. If the load is so great that this 12 volt power source is insufficient to turn the engine of the stalled vehicle fast enough to start the engine, the two 12 volt batteries are then placed in series, thereby providing a nominal 24 volt power source. This power is usually sufficient to start the stalled vehicle engine. However, if the load created by the stalled vehicle engine is not sufficient so as to require a 24 volt power source, and if the two 12 volt batteries are placed in series to provide the 24 volt power source anyway, excessive voltage and current applied to the stalled vehicle could cause severe damage.